It is known to use powered portable sanders or grinders utilizing flexible, abrasive grinding discs, These sanders can be used for finishing a plurality of surfaces such as wood, metal, plastic or other materials, When used, the discs generate upon surface contact a considerable amount of dust and debris made up mostly of the material being sanded, Such materials, especially some toxic plastics, if not controlled to an extent, could cause a serious health problem to the operator, There have been many structures designed to protect the operator from body contact with the residual dust particles which are generated during the sanding or grinding operation. Most of these apparatuses contain vacuuming equipment or components to immediately remove the dust or debris as it is generated by the disc, Thus, these powered, sanding apparatuses require protective shields or components for the collection and containment of dust and particulate matter generated during the sanding or grinding operation,
Some of these aparatuses are disclosed in U.S. Pat. Nos. 3,882,644; 4,422,239; 4,616,449; 4,622,782; 4,624,078; 4,765,099 and 5,125,190, In U.S. Pat. No. 3,882,644 (Cusumano) a dust-extracting device is disclosed having a vacuum or suction conduit with a brush guard encircling its sander disc. The Cusumano apparatus is similar to those that have been used in the prior art. The brush used by Cusumano is connected to his truncated, circular hood by the use of material connecting strips which are secured outside the sander skirt. The brush guard and arcuate skirt surrounding his sanding disc are conveniently used components that assist the vacuuming of generated dust particles. The plane level of the hood roof 28 and ring clamp of Cusumano's structure are above and substantially parallel with the lower contact surfaces of his bristles 68. This feature could permit the escape of debris from under the bristles when the sander is press-tilted forward during the sanding operation.
In U.S. Pat. No. 4,422,239 (Maier et al) a powered handtool is disclosed having suction means 100. His suction means are designed running from the cover into and through the housing so that there are no flexible pipes joined up with the cover. Maier does not show a brush skirt to be used with his handtool.
Roestenberg, in his U.S. Pat. No. 4,622,782, discloses a sander shield having a plurality of vacuum holes each connected to one end of a vacuum hose and vacuum pump. In this manner, Roestenberg can reach every part of the interior of his sander as the dust is generated. Roestenberg does not utilize a brush skirt or brush shield.
In U.S. Pat. No. 4,624,078 (Van Rijen) a surface sander is disclosed having a dual dust hood enclosing the motor housing. The dust collector hood of Van Rijen acts as both a receptacle for dust extraction and as a mounting means. A flesible skirt 21 is fastened to the lower rim of Van Rijen's apparatus. However, by extracting dust particles through holes 53, his skirt 21 may be dispensed with.
Marton, U.S. Pat. No. 4,616,449, discloses in his patent a suction housing for vacuum sanding devices. The suction plate is formed of a relatively flexible plastic material. A flexible skirt is also used by Marton to assist in removing or collecting process-generated dust from the situs.
In U.S. Pat. No. 4,765,099 (Tanner) a sanding and dust-collecting apparatus is disclosed which allows collection of dust residue without the requirement of vacuum equipment. Tanner uses a one-piece brush assembly 20 which forms a flexible dust containment curtain about the sanding disc assembly 50. The brush assembly 50 of Tanner's device is constructed so that its upper end portion 94 is parallel with the terminal ends 52 of brush 22.
In Buser, U.S. Pat. No. 5,125,190, a shield attachment for fitting on a rotating grinder is provided which shields the rotating disc. Buser's shield provides a tangential exhaust port for exhausting dust in moving air created by the rotating disc. Buser's hood 10 is generally constructed of molded plastic or fiberglass and has a lower circular edge portion 26 that is in a single plane substantially parallel with the upper surface 20 of the shield.
In all of the above prior art units, the collars or ring attachments that connect a shield or skirt to the sander structure are generally of one size and thus are suitable only for one size sander. Also, the lower terminal end of prior art shields, whether bristles or other flexible means, are substantially parallel with the ring attachments and the upper roof section of the shields. This type shield construction could readily cause the shield to lift above the grinding plane at a location opposite to the locus of the exerted pressure. Any space between the shield and the surface being sanded could permit significant amounts of dust and debris to escape to the atmosphere and expose the user to substantial safety problems, in particular when sanding toxic surfaces.